Information recorded on a recording medium can be written into a predetermined area on a face opposed to a recording face of the circular shaped recording medium such as a CD-R. As an example of a recording apparatus for printing on the area, international patent application no. PCT/JP96/02833 discloses a recording apparatus in which the recording medium is set on the tray for transfer, the tray for transfer is transferred, and printing is performed. The recording medium is set in a shallow circular recess formed at a center part on a surface of the tray for transfer formed by a thin rectangular board of the tray for transfer, the tray for transfer holding the recording medium is transferred by a transfer roller, and printing is performed on the recording medium's surface using a recording head.
However, in a conventional recording apparatus, there is no mechanism for distinguishing the surface of the transfer tray from the back face of that tray, meaning that printing can be accidentally performed on the back face of the transfer tray when the surface and the back face of the transfer tray are inadvertently reversed and the transfer tray is erroneously transferred with the tray's faces in the reversed orientation.
As a result, the attendant waste causes the consumption of additional ink and such extra use causes ink to spill on the back face of the tray for transfer. The surface of the material of the rectangular transfer tray is uneven and some warping or deflection easily occurs in the tray. Recording precision diminishes due to this warping or deflection.
When the end of the transfer tray passes over the transfer roller, a driving roller abuts against the following roller, since the transfer tray is a rectangular board having a given thickness. This causes noise. Therefore, according to one aspect of the present invention, printing on a transfer tray is prevented, inferior print quality due to warping or deflection is reduced, and less noise arises as the tray is transferred by the transfer mechanism. Consequently, printing on a label face is efficiently carried out with high print quality and lower noise.
An ink jet type recording apparatus exists with a transfer tray holding a recording medium such as a CD-R. The transfer tray is inserted into a hand-feeder passage in a manner similar to an inflexible recording sheet like cardboard and the tray allows recording to be carried out on a label face of the recording medium.
The ink jet recording apparatus includes a carriage mounted on a recording head, which moves reciprocably in the main scanning direction, and a recording medium transferring mechanism for transferring the recording medium in the sub-scanning direction. The ink jet type recording apparatus records on recording paper fed from an auto feeder apparatus and also has a hand-feed passage for feeding cardboard, etc. by hand in place of the auto feeder apparatus. The ink jet type recording apparatus is capable of recording on the transfer tray that supports the recording media in the same manner as cardboard. When the transfer tray of such an ink jet type recording apparatus is inserted into the transfer passage by hand, it is difficult to determine the position of the tray accurately. Therefore, printing on the recording medium is performed at a position that is slightly off. This is because a positioning mark to be set when the transfer tray is set to an accurate position of the ink jet type recording apparatus or the transfer tray is not indicated on the ink jet type recording apparatus or the tray for transfer. Thus, recording is not carried out as expected.
For the user to set the transfer tray at the accurate position, it is necessary that the accurate position be maintained by repeatedly setting the tray, recording the accurate position in a memory, or otherwise indicating any marks.
Accordingly, the second object of the present invention is to provide a transfer tray which can easily be placed at an accurate position when a tray transferring a sheet to be recorded is loaded into an ink jet type recording apparatus.
In an ink jet type printer, paper or other recording media is fed from an auto sheet feeder or an inlet by hand and is sandwiched between a main driving paper feed roller and a follower roller. While the paper feed roller is rotating, pressure is applied to ink in a pressure generation chamber of the recording head and ink droplets are ejected from a nozzle opening causing images to be printed on the recording paper.
In the paper feed mechanism of the printer, paper is placed in the start position and the printing operation is performed with reference to this position. Therefore, it is necessary to position the leading edge of the paper with high precision. In a conventional device, the paper feed is stopped when the detected output from a light-emitted element changes in voltage according to whether or not the paper is present. By exceeding the value, the transfer of paper is stopped and the leading edge of the paper is moved forward.
FIG. 35 depicts an optical sensing element often used when the leading edge of paper precisely moves forward. A reverse V type slit is formed on the lower face of the optical sensor 722. A light-emitting diode 723 and a photo-diode 724, respectively, are provided on a slit facing each other. Light generated by the light emitted diode 723 is irradiated onto the recording paper 745, reflects off of the paper and is detected by the photo-diode 724.
FIG. 36 is a graph depicting the change in an output voltage of the photo-diode 724 when paper is fed from the left-hand to the right-hand side past the detector arrangement shown in FIG. 35. The graph shows a voltage value on the vertical axis and the amount of transferring paper counted by an optical encoder is shown on the horizontal axis.
FIG. 37A depicts the state where there is no paper and FIG. 37B shows the state where there is paper for the graph of FIG. 36. FIG. 37A shows a state prior to the transfer of the recording paper 745 to change of the optical sensor 722. That is, a state where the optical sensor 722 measures reflected light just from the structure of the paper feed passage (e.g., a paper guide board or paper feed roller). In contrast, FIG. 37B shows tho state where paper moves forward, the paper is positioned under the optical sensor 722, and the photo diode 724 receives only the light reflected from the paper.
Once the end of the recording paper 745 is within a range that can be detected by the optical sensor 722, the output voltage of the photo diode 724 goes up and exceeds a predetermined voltage value shown by the dotted line in FIG. 36 at a position depicted in FIG. 35. A count value in this case is indicated as CO.
However, it is difficult to detect the position accurately. This is because it is difficult to tell when the output of the photo diode 724 exceeds the predetermined value because that value depends on the type of paper inserted in the printer. As a result, the quality of the printed output for a particular printing medium will vary depending on the surface properties of that printing medium. Some examples of the printing media that can be used include high quality, coated, inkjet printer paper, rough surface papers, etc.
Recording papers used in conventional inkjet printers include thin paper such as standard paper or specific-use paper for high quality color printing, cardboard, and slightly thicker paper such as label paper which has adhesive material on one side. Therefore, the range of brightness by paper classification is not very large.
Recently, recording paper which is thicker than conventional cardboard has also been used in full color printing.
On the other hand, an optical disk recording medium capable of being written, such as CD-R (Compact Disk Recordable) or CD-RW (Compact Disk Rewritable), is widely used by individuals. Commercially, label printing is performed on a thin adhesive printing label.
If printing can be applied directly to an optical disk surface, it is both convenient and solves the problem arising where the label is removed.
To enable direct printing on an optical disk, a transfer tray made of polypropylene has been designed so as to hold the disk. The thickness of that transfer tray is about 2.5 mm.
There is a need to use a transfer tray to hold board paper or an optical disk in the paper feed mechanism of a printer when printing is performed on such a recording medium, it is not appropriate to use the auto sheet feeder as described, but rather, the medium is conveyed from an inlet using the hand feeder.
When such recording media are inserted into the feeder mechanism of the printer from the inlet, owing to the fact that these media may differ in thickness, problems may arise.
When the transfer tray holding the optical disk is transferred to a detection mechanism similar to the detection mechanism described in FIG. 35, 36, 37, the conditions in the printer may vary. FIG. 38 shows the relationship between the optical sensor 722 and the transfer tray 746. The transfer tray 746 is thicker than the general recording paper. Because of the thickness of the recording paper 745, light generated by the light emitted diode 723 is illuminated on the side of the transfer tray 746. Due to the influence of the beveled edge on the upper part of the transfer tray, light emitted by the light emitted diode 724 is reflected along the paper feeding passage. This reflection results in the diffusion of light, which cause a different behavior in the operation of the photo diode 724. Thus, the resulting operation of this example differs from the operation of the example shown in FIG. 36.
FIG. 39 shows a graph indicating output voltages of photo diode 724 when the transfer tray 746 is fed. Due to diffusion, output voltages increase slowly. But when the inputs are increased, accordingly the output increases in a concave manner. For example, when a transfer tray holding an optical disk is guided into the paper feed mechanism of a printer system, it is desirable to be able to control movement of the transfer tray so that the aforementioned end of the recording mechanism moves forward with precision and in a manner that does not depend on the type of recording medium used, even when the end of the recording medium is detected by using a reflection type optical sensor.
According to a third aspect of the present invention, the structure holding the recording medium can advance the end the recording medium with high precision and in a manner independent of the kind of recording medium used, even when the end of the recording medium is detected by using the reflection type optical sensor.
FIG. 40 is a perspective view showing the arrangement of an optical sensor 722 in a conventional ink jet printer, as well as aspects of the paper feed structure located inside the printer. In this example, an auto sheet feeder is attached to the printer for sending paper into the paper feed path. The structure for storage of the recording paper 745 is not shown in this example. The optical sensor 722 has detection elements as already discussed located on its bottom face. The sensor 722 is mounted between an auto sheet feeder (ASF) roller 750 driven by an ASF motor 711 and a feeder side roller 751 driven by a paper feed motor 712.
In this example, the ASF roller 750 does not start feeding recording paper 745. Thus, the recording paper is out of range for scanning with an optical sensor 722. Therefore, the optical sensor 722 detects reflected light only from the structure of the apparatus forming the paper feed path (although not shown, this includes the paper guide board or the feed side roller 751). Therefore, the output voltages in FIG. 36 represent voltages, Vn, measured when there is no paper.
The example shown in this Figure includes a photo sensor having a light-emitting diode and a photo-diode, and feeds paper along the print feed passage. In this configuration, the output voltage of the photo-diode is observed. FIG. 36 shows a diagram of the output voltage of the photo-diode 724 measured with respect to the count number, C0, and the values determining the location of paper for a particular configuration are shown in FIG. 35. In this arrangement, as shown in FIG. 36, the output voltage of the photo-diode stays at Vn, which signifies that the loaded paper is located outside of the range of the photo sensor. Once the end of the recording paper 745 is within the detection range of the optical sensor 722, the output of the sensor starts increasing with the voltage of the photo diode 724. Then, when the loaded paper is fully in range of the sensor, the voltage reaches the its highest value, V1. During this voltage change, the voltage passes a predetermined value set for determining the location of the loaded paper.
Then the paper continues feeding and the configuration changes to that shown in FIG. 41. The output voltage of the optical sensor 722 is V1 as shown in FIG. 36. The value V1 represents a voltage showing that the feed paper exists in all ranges.
In this manner, it is difficult to maintain high measuring precision. Thus, to improve the procedure, the applicant has developed a technology that more accurately moves the leading edge of paper forward at the same position even when paper having different brightness is used. (See Japanese Laid-open publication No. 9-136741). Differences in the value of a voltage between the state where there is no paper and where there is paper is all that is required to determine the position of the paper. In this prior art, the arrival of the leading edge of the paper is determined by using derivatives of particular voltage values and particular coefficients.
In the prior art, after the recording paper 745 is in the detection range of the optical sensor 722, the paper is moved forward. The recording paper 745 is then retracted from that position until the paper is not detected by the sensor.
When operating in this manner, it is inconvenient to mount the optical sensor 722 at the aforementioned position. For example, to retract the recording paper 745 from the position shown in FIG. 41 to the position shown in FIG. 40, the paper feed motor 712 must be rotated in the reverse direction and the ASF motor is synchronized to be rotated in a reverse direction, or the driving mechanism is released.
Consequently, the ASF roller 750 freewheels. After recording paper 745 separates from the feeder side roller 751, it is also necessary to retract the paper by reversing the ASF motor.
In the case where paper is supplied from the hand feeder inlet 751 another problem arises. This is because the apparatus has a mechanism to pull back additional fed paper after the recording paper 745 separates from the feed side roller 751. A separate simultaneous mechanism is required.
As described above, it is not desirable to drive two or more motors for withdrawing the paper because the operational control required for multiple motors becomes complicated.
Further, the arrangement of the optical sensor 722 may raise a problem with respect to the accuracy of the paper heading operation. As shown in FIG. 41, the actual position of the leading edge of the paper when the printing is actually performed is located ahead of a position of the recording paper 745. That is, at least the leading edge of the recording sheet 745 must be positioned ahead of the carriage 713 on which the recording head is mounted. If the position of the leading edge of the paper detected by the sensor is far from the position of the leading edge of the paper when the printing operation is actually performed, it is more likely that there may be an undesirable deviation in the paper feed or, in the worst case, a paper jam.
Accordingly a fourth object of the present invention is to perform accurately the operation of the paper feeding and reverse paper feeding as mentioned above by reviewing the placement of the optical sensor within the paper feeding path. Further, another object of the invention is to provide a technique which can achieve these operation using a motor control which is less complicated than a conventional motor control.
In addition, with printers today using several different kinds of recording paper, more accurate control has been required.
For example, in an ink jet type printer in which fine ink droplets are ejected from nozzles arranged on a recording head to record dots on a recording paper, the recording head does not contact the recording paper. A gap of approximately 0.6 mm must be left between the head and the paper.
Accordingly, so that the ink jet printer can produce dots having the desired diameter, the gap between the head and the recording paper must be kept constant even when different thicknesses of recording paper are used. For that reason, recent ink jet manufacturers have installed a mechanism for adjusting the gap between the head and the paper.
In the ink jet printer or the like, the recording paper is put on a flat plate (platen) which guides the paper while keeping the paper in a horizontal orientation, and printing is performed in a space above the platen by scanning the carriage on which the recording head is mounted. Accordingly, the gap adjustment mechanism regulates the gap between the nozzle opening and the platen, i.e., a paper gap, by moving the carriage up and down.
The recording media which the conventional ink jet printer can handle include thin paper having a thickness equal to or less than 6 mm such as normal paper, special purpose paper for high-quality color printing, and thick paper having a thickness between approximately 0.7 mm and 1.5 mm, such as an adhesive label sheet.
In order to allow direct printing onto an optical disc, a transferring tray made of polypropylene is used to hold the optical disc. The transferring tray has a thickness of approximately 2.5 mm and, therefore, a large adjustment for the paper gap is required. The printer, which is capable of printing on the optical disc, has a mechanism for manually setting the paper gap to compensate for the thickness of the transferring tray.
In the conventional apparatus, thin paper is fed by an automatic sheet feeder while thick paper is fed from a manual paper-feed slot. Thus, different kinds of paper move through different paper feed paths. Therefore, an erroneous setting of the paper hardly occurs. However, both the thick paper and the transferring tray, which can be treated as a piece of extremely thick paper, are fed through the same manual paper-feed slot. Therefore, it is likely that a user may select the incorrect paper gap.
Therefore, the fifth object of the present invention is to provide a printer which is capable of detecting an error in the gap setting, and which takes steps to resolve the problem by suggesting that the user reset the paper gap.
Generally, an ink-jet type recording apparatus is provided with a paper feed roller 1040 for feeding a recording medium P such as printing paper to a recording region 1051 where a recording head 1100 is located and a paper discharge roller 1010 is provided for discharging the paper that has been recorded in the printing region 1051. In this operation, the paper discharge roller 1010 includes a row of rollers arranged in the main scanning direction in the widthwise direction of the recording medium P at a position downstream in the sub-scanning direction of the recording region 1051 of the printing apparatus, that is, the feeding direction of the recording medium P. The paper discharge roller 1010 is made up of a paper discharge driving roller 1011 and a paper discharge following roller 1012. The paper discharge following roller 1012 may be a roller having teeth arranged on its periphery, and the teeth can be sharp and come into contact with the recording surface of the recording medium P. The roller is mounted in such a manner that the teeth are exposed both on the top and bottom, although this is not shown in FIG. 47. Further, at a position further downstream of the paper discharge roller 1010 in the sub-scanning direction, there is located a discharge roller 1060 which is rotated by the feeding force of the recording medium P. The term paper discharge following roller is used in the present description to describe the paper discharge following roller 1012 and the discharge roller 1060 shown in FIG. 47. Therefore, the paper discharge following roller represents either the paper discharge following roller 1012 and/or the discharge roller 1060.
By the way, it may occur that the ejection follower roller, which rotates as a result of contact with the recording medium, becomes slightly inclined during the transportation of the recording medium, to either the right or left from a position where the teeth are perpendicularly contact with the sheet of paper. When a change of angle (inclination) occurs, the ejection follower roller does not smoothly rotate. Therefore, the teeth of the ejection follower roller which are in contact with the recording media make fine marks or scratches on the printing surface of the recording medium, which reduces the quality of the recorded product.
Particularly, in cases where a sheet of recording media has a printing surface coated with a chemical, resin, or the like (“a coated sheet”) is used as a recording medium, the printing surface of the coated sheet is so delicate that contact between the teeth and the sheet might make fine marks on the surface of the coated sheet even if the rotational direction of the ejection follower roller is parallel to the transporting direction of the recording medium (also referred to hereinafter as a “parallel position”, when applicable). Accordingly, the contact of the teeth with the sheet should be prevented as much as possible.
If the teeth make contact with the coated sheet while the teeth are inclined away from a right angle, the coating layer peels slightly, forming raised areas around the aforementioned recesses (so-called “pickings”). If the pickings are formed on a high quality printing job like a picture, the quality of the final picture deteriorates.
Often, such peeling or pickings of the coating layer results from the reverse rotation of the ejection follower roller. For example, when printing on a continuous recording medium such as roll paper, a cutter, which cuts off the recording medium after printing, is placed downstream in the transporting direction from the ejection roller. In this case, it is necessary to feed back the roller paper by a certain amount upstream in the transporting direction. Accordingly, the rollers mentioned above are rotated in reverse. If any peeling or pickings are formed during the reverse rotation, this may have a large effect on the printing quality.
Furthermore, beyond the problems of peeling and pickings, depending on the purpose for the recording, it is convenient for a user to adjust the ejection follower roller such that it stays away from the surface of the recording media.